Problem about the ionic conductivity

Hi...

I am a novice of MD simulation.

My project is concerned with ionic conductivity of polymer electrolyte systems.

I tried to calculate the ionic conductivity from the mean square displacement using Forcite+ MD.

But it is a self diffusion coefficient.

From the literature (Muller_Plathe, Gunsteren, 1995, JCP, Computer simulation of a polymer electrolyte Lithium iodide in amorphous poly(ethylene oxide)), the ionic conductivity is not a self but a correlated measure with other particles.

The equation is

ionic conductivity.JPG

Could this equation be calculated with Forcite+ or Mesocite?